This investigation is designed to evaluate the combined anti-tumor action of the complement and humoral antibody systems during the early stages of a host's response to its syngeneic neoplasm. The experimental model will be based on the growth of the (C58NT)D Gross Virus-induced lymphoma in W/Fu rats. A singular feature of the experimental approach involves the estimation of early anti-tumor antibodies in the lymphomatous host on an absolute weight basis. A method capable of performing these assays, the CFAA, has been used successfully, as described in the text, for studies of the primary immune response to soluble and cellular antigens. The values obtained with this procedure will enable us to express the biological activities of the IgG and IgM tumor-induced immunoglobulins on a weight specific basis. We have also observed that W/Fu rats, essentially depleted of C3 and the later complement components, are more susceptible to the (C58NT)D lymphoma cells. Intraperitoneal multiplication and mortality rates are increased in the decomplemented rats. Furthermore, the sera of these animals are less efficient in mediating one phenomenon of cellular immunity, the antibody-dependent cellular cytotoxicity, ADCC. The research plan describes a series of experiments aimed at defining the mechanism of tumor cell growth modulation by antibody and complement. These will include studies of the role of complement-depletion on anti-tumor antibody synthesis, on quantitative definition of the molecular events in ADCC and adoptive immunity, on the level and significance of circulating immune complexes, on macrophage function and on several in vivo activities of the (C58NT)D lymphoma cells.